The present invention pertains to conveyors, and, in particular, to an electrically-powered control system for controlling an accumulating conveyor.
Accumulating conveyors are well known in the art. These conveyors are divided into zones, and various types of controls are used to control the driving of the zones. The purpose of these types of conveyors is to convey articles smoothly without the articles bumping into each other and crushing each other when there is a back-up or delay in the system. Thus, when there is a back-up in the system, some zones will stop driving and will permit the articles to accumulate on them until the back-up is cleared and the articles can again be conveyed along the conveyor's path. In the past, mechanical controls have primarily been used in these systems. For example, a sensor bar will be located along the conveyor, and, when the bar is depressed, it will close a valve or trigger some other type of mechanical control which will cause the drive for the next zone to be disengaged. These mechanical systems have several drawbacks. For example, if the article is not heavy enough to depress the sensor bar or has an irregularly-shaped bottom which does not depress the sensor bar, the system will not sense that the article is present and will not cause the next zone to stop driving. Also, the mechanical systems include many moving parts which require a considerable amount of maintenance.
Electronic controls are also known. These systems sense the presence of an article by electronic means, such as by means of a photo-electric sensor. The use of a photo-electric sensor instead of a mechanically-operated sensor bar eliminates the problem of the system failing to be triggered if the article is not heavy enough. The electronically-operated system using a photo-electric sensor will sense the presence of any article which stops the transmission of light. The photo-electric-controlled systems now being used include a central processing unit, and each photo-electric sensor communicates with the central processing unit or "brain" of the system. The central processor makes the decision as to which zones should be driven and, in turn, communicates with a solenoid in each zone, telling each solenoid whether to engage or disengage the drive for its zone. This type of system requires extensive wiring and a sophisticated central processing unit. It also requires fairly sophisticated diagnostics to analyze the location of a problem in the event that there is some malfunction in the system.